Graded multiphase carburized materials

ABSTRACT

A carburized, multiphase material formed of at least one metal of each of Group I, II, and III. Group I is columbium, tantalum, and vanadium; Group II is titanium, zirconium and hafnium; and Group III is molybdenum, tungsten, rhenium and chromium. Have excellent abrasion resistance.

United States Patent Van Thyne et al.

[ Aug. 20, 1974 GRADED MULTIPI-IASE CARBURIZED MATERIALS Inventors: Ray J. Van Thyne, Oak Lawn; John J. Rausch, Antioch, both of 111.

Assignee: Surface Technology Corporation,

Stone Park, 111.

Filed: Apr. 10, 1972 Appl. No.: 242,857

Related US. Application Data Division of Ser. No. 99,366, Dec. 18, 1970, Pat. No. 3,713,907.

US. Cl 148/315, 51/309,148/203 Int. Cl C2ld 9/22, C23c 11/14 Field of Search 148/203, 31.5, 32; 75/134, 135, 174, 175.5, 176, 177, 201, 203, 208, 212; 29/1822, 182.5, 182.7; 51/309 References Cited UNITED STATES PATENTS 2/1962 Lottridge et a1. 75/174 12/1964 Douglass et a1 148/39 X OTHER PUBLICATIONS Belgian Patents Report No. 10/69, 7:Meta11urgy p. 1 No. 720393 & 720399.

Primary ExaminerChar1es N. Lovell Attorney, Agent, or Firm-Albert Siegel [57] ABSTRACT A carburized, multiphase material formed of at least one metal of each of Group 1, II, and III. Group 1 is columbium, tantalum, and vanadium; Group 11 is titanium, zirconium and hafnium; and Group III is molybdenum, tungsten, rhenium and chromium. I-lave excellent abrasion resistance.

19 Claims, 6 Drawing Figures 3.830.670 sum 10F 2 l MIL.

SCALE: 0J5 INCHES I MIL.

PAIENH-Iummmen 8HEEI 20F 2 SCALE GRADED MULTIPHASE CARBURIZED MATERIALS This is a division of application Ser. No. 99,366 filed on Dec. 18, 1970 now U.S. Pat. No. 3,713,907 dated Jan. 30, 1973.

BACKGROUND OF THE INVENTION Our invention is directed particularly to carburized materials of selected alloy compositional ranges which are characterized by a graded microstructure and as having excellent abrasion resistance. Such materials are and must be continuously graded from the surface inwardly in terms of microstructure, hardness and carbide concentration. The alloys required in order to obtain such grading and desired properties are ternary or more complex. The use of refractory metal alloys carburized as hereindescribed results in very substantial abrasion resistance especially as compared with carburized ferrous alloys.

The alloys which we carburized contain certain of th refractory and reactive metals of Groups IVB, VB, and WE of the Periodic Table of Elements. We have discovered that when the present alloy systems are carburized there results the surprisingly good properties and related graded microstructure set out below.

In the present specification and claims much usage is given to the terms phase and multiphase. We employ said terms as they are commonly used in good metallurgical practice. By phase we mean a physically homogeneous and distinct portion of a materials system and by multiphase two or more coexisting phases.

We would note obviously that the carburizing of certain metals or alloy systems is not novel and further that certain of the unreacted base alloys which are employed in the present invention are also not novel. Furthermore alloy compositions fairly similar to ours with relatively small carbon additions used principally for strengthening have also been reported. However, nowhere does the prior art show the graded materials with the resulting excellence as are set forth below.

The carbides of the metals of Groups IVB, VB, and WE are known to have high hardness, corrosion and oxidation resistance and high melting points. Methods for utilizing these properties for either wear resistance or strengthening have been studied by numerous investigators over a period of years and such studies have included carburizing, powder processing techniques and the dispersion strengthening of various alloy matrices.

ln the dispersion strengthening art, a relatively low volume of fine particles is distributed essentially uniformly throughout an alloy. Carbides have been favorite agents in dispersion strengthening of refractory metal (i.e., Cb, Ta, V, Mo, W base) alloys particularly for improvement in creep rupture properties. See, for example, U.S. Pat. Nos. 2,822,268 and 3,194,697, and Canadian Pat. No. 716,520. Whereas very significant creep strengths can be obtained, the volume of hard phase is low and these dispersion strengthened alloys do not at all compare to the extreme abrasion resistance demonstrated by the materials of the present invention.

Other investigators have also attempted to make multiphase wear products by a variety of powder processing techniques which consist essentially of dispersing carbides in a matrix of refractory metals or alloys. These investigators correctly assume that replacing the cobalt binder used in commercial sintered carbide with a higher melting matrix would enhance wear resistance, but such materials are made only under the most laborious conditions since it is very difficult to achieve full density. Such wear products may contain a relatively high volume of hard phase uniformly dispersed but they are not produced by external carburizing and are quite different from the materials of our invention. The structures obtained are not graded from the surface inwardly as is the case with our materials.

Patents directed to the carburizing of elemental tantalum metal have issued from at least 1908 (See U.S. Pat. No. 896,705) to the present. (See U.S. Pat. No. 3,523,044 of 1970). These inventions disclose the formation of continuous carbide layers at the surface which we specifically reject as having inferior utility and which in no way form a part of the present inventron.

The tendency of the carburized layer on elemental metals to crack and delaminate at the carbide-metal interface and spall was reduced by alloying prior to carburizing and resulted in an irregular interlocking interface. (See U.S. Pat. No. 3,163,563). In this referenced invention the carbide layers are similar to carburized tantalum and an important feature thereof is the formation of a thicker layer of the outer carbide. The patentees objective of a relatively thick outer carbide layer differs quite substantially from our present invention in that the carbide zone in our materials is not continuous. The formation of the irregular serrated boundary between the carbide layer and the substrate may improve adherency somewhat. However, the elimination of a relatively thick continuous carbide layer in favor of a multiphase graded structure as we teach in this present invention results in greatly improved properties in our materials.

Those skilled in the art will recognize that in addition to carbon, boron and nitrogen may also be employed as hardening agents in refractory alloys. In our copending applications, Wear Resistant Materials Ser. No. 755,658 now U.S. Pat. No. 3,549,427 and Wear and Abrasion Resistant Materials Ser. No. 755,662 now U.S. Pat. No. 3,549,429 (counterparts have now issued as French Pat. Nos. 1,584,635 and 1,596,561 we have disclosed how to prepare graded nitrided materials. These are ternary or higher order alloys and a necessary requirement of those systems is the presence of molybdenum and/or tungsten to achieve the desired degree of relative reactivity with nitrogen since both molybdenum and tungsten are essentially inert in nitrogen.

Unlike as in the nitrided systems, molybdenum or tungsten are quite active in a boronizing or carburizing environment and form very hard, stable compounds. We attempted the boronizing of a variety of compositions that yield useful nitrided materials including a1- loys of columbium or tantalum with titanium or zirconium, and with up to 20 percent molybdenum or tungsten. However, in such materials only continuous surface boride layers form thereon. Thus, it was with some considerable surprise that we discovered that similar compositions exhibit the desirable relative reactivity with carbon and form graded multiphase composites with carbide content and hardness lessening as one moves deeper into the material from the surface. Furthermore, we have found that the carburized materials show certain differences and advantages over nitrided materials as demonstrated in the subsequent examples. The physical stability of the carbides is greater than that of the nitrides. The nitrides can exhibit a significant vapor pressure at the reaction temperatures of interest.

In distinction to all of these prior art teachings as will be apparent to those skilled in the art, we have developed a graded, multiphase series of composite structures which are further characterized by excellent wear and abrasion resistance properties.

DESCRIPTION OF THE INVENTION In the preferred embodiments of the present invention certain ternary or higher alloyed systems are carburized. Such alloy systems consist of metals of Groups I, II and III wherein:

Group I is one or more metals of the group columbium, vanadium and tantalum;

Group II is one or more metals of the group titanium,

zirconium and hafnium, and

Group III is one or more metals of the group molybdenum, tungsten, rhenium and chromium.

A principal object of our invention is to produce a novel group of carburized, multiphase structures consisting of carburized alloys of Groups I, II and III.

Another object of our invention is to provide such novel materials wherein a portion of the carbides are replaced by either nitrides or borides or both.

These and other objects, features, and advantages of our invention will become apparent to those skilled in this particular art from the following detailed disclosure thereof and from the enclosed FIGS. 1 through 6 which are photographs of 150X magnification in which:

FIG. 1 shows Ta-30I; gas carburized at 3,250 F for 2 hours;

FIG. 2 shows Ta-20Tl-l0Mo gas carburized at 3,350 F for 2 hours;

FIG. 3 shows unalloyed columbium pack carburized at 3,450 F for 2 hours;

FIG. 4 shows Cb-70Ti gas carburized at 3,250 F for 2 hours;

FIG. 5 shows Cb-40Ti gas carburized at 3,250 F for 2 hours; and

FIG. 6 shows Cb-20Ti-40W gas carburized at 3,350 F for 2 hours.

The alloys which were carburized were melted under an inert atmosphere in a non-consumable arc furnace using a water-cooled hearth. The alloy specimens were gas carburized in an atmosphere of either methanehydrogen or methane-argon using high purity gases with a methane content under 10 percent or pack carburized by embedding in chunk carbon and heating in an atmosphere consisting of 95 percent argon 5 percent hydrogen. Gas carburizing results in a smoother surface, particularly at the higher titanium compositions.

Many ternary alloys were carburized and then evaluated metallographically. A number of examples of compositions falling within our invention are presented in Table I. All of said compositions have a multiphase, graded composite structure essentially to the surface and because of a high volume of hard phase near the surface demonstrate good abrasion resistance. For effective wear resistance, materials of the present invention should contain at least 25 percent by volume of hard phase at the surface. Our carburized materials contain substantially more than 25 percent hard phase at the surface. The multiphase structure minimizes chipping and by imparting toughness contributes to high performance.

In the present specification and claims allcompositions are given in weight percent.

TABLE 1 COMPOSITION CARBURIZATION (W/O) (F) (Hours) (Type Cb-20Ti-20Mo 3450 2 G Cb-30Ti-l0M0 3350 2 G Cb-30Ti-20Mo 3350 2 G Cb-4OTi-30Mo 3450 2 G Cb-30Ti-20W 3350 2 G Cb-40Ti-40W 3350 2 G Cb-l0Ti-l0Mo 3250 7 P Cb-l7Ti-20W 3250 6 P Cb-l7Ti-20W 3450 2 P Cb-30Ti-20W 3250 8 P Cb-20Ti-40W 3250 7 P Ta-2OTi-l0Mo 3350 2 G Ta-30Ti-20Mo 3350 2 G Ta-35Ti-3SMO 3350 2 G Ta-20Ti-20W 3450 2 G Ta-40Ti-30W 3450 2 G Ta-IOTi-IOMQ 3250 6 P Ta-IZTi-ISW 3250 6 P Ta- I 8Ti-25W 3250 6 P Ta- 1 8Ti-25W 3450 2 P V-27Ti-l0Mo 2950 2.5 G V'24Ti-20M0 2950 2.5 G V-20Ti-30Mo 2950 2.5 G V'-20Ti-1OW 2950 2.5 G V24Ti-20W 2950 2.5 G V5Ti-50W 2950 2.5 G Cb-20Ti-40W 3350 2 G Cb-30Zr-l0Mo 3250 2 G Cb-20Zr-20W 3250 7 P Cb-IOZr-SSMO 3250 7 P Cb-30Hf-l5W 3250 7 P Cb-20Ti-20Re 3250 7 P Ta-25Til 5R0 3250 7 P Cb-30Zr-20Re 3250 7 P Cb-20Ti-25Cr 2850 6 P Cb-20V-40Ti-l0Mo 2950 2.5 G Cb-30Ta-l0V-l0Ti-l0Zr-5M0-5W 3250 7 P Cbl5Ti-l5Hf-20W 3250 7 P Cb-25Ti-l0Mo-l0Rc 3250 7 P G Gas carburized using methane-hydrogen or methane-argon. *P Pack carburized using chunk and A-5/( H FIG. 1 shows a carburized binary alloy, Ta-30Ti, with a thick continuous carbide layer similar to that formed on carburized tantalum and obviously is excluded from our invention. The resulting difference in carburizing of a ternary alloy, Ta-20Ti-l0Mo is shown in FIG. 2 an improved structure that is included in our invention. A thick surface carbide is illustrated for unalloyed columbium and Cb-Ti in FIGS. 3 and 4, respectively. After carburizing a range of Cb-Ti compositions, we find that at a composition of Cb-40Ti a coarse twophase structure is formed under the continuous surface carbide (FIG. 5). The significant modification in structure achieved by addition of a ternary constituent prior to carburizing is seen in FIG. 6, representing Cb 20Ti- 40W. Other microstructural forms are seen in other carburized materials within our invention but in all examples such structures are multiphase and grade inwardly. The precipitated phases shown in FIGS. 2 and 6 form from single phase solid solutions during carburizing. Preferrential segregation of carbon and titanium into the precipitated hard phases was shown by microprobe analyses of carburized Ta-l2Ti-l5W.

By the term graded as used regarding carbide formation in the present specification and claims we mean that there is a lessening of metal carbide formation and thus concentration as one moves inwardly from the surface. Such grading is shown in FIGS. 2 and 6.

The good grading in our carburized materials is also demonstrated by microhardness (DPN) readings on the 5 flat surfaces of metallographically polished cross sections. For one-eighth inch thick materials falling within our invention the gram load hardness measured on a cross sectional traverse in a zone between the surface and a depth of 0.5 mil is at least 800 DPN and the hard- 10 ness grades inwardly in a mostly continuous fashion. Selected data using a 50 gram load at 0.5 mil and a 200 gram load at l to 8 mils from the surface are given in Table II.

mation of continuous carbide layers and Ta-10Hf and Ta-10W carburized at 4,170 and 4,530 F were two of the examples used in that specification. Temperature may be expected to play a role in microstructural relationships. Accordingly, we carburized these two compositions at a lower temperature (3,250 F) but con- Both carburized columbium and Cb-70Ti show cracking around the hardness impressions in the hard continuous carbide layer and an abrupt change in hardness between the outer carbide layer and the substrate whereas grading and support of the hardened surface is evident in the three materials in Table II included in our invention. Our materials can exhibit very high hardness near the surface. The 50 gram micro-hardness at a depth of 0.3 mil from the surface was 4350 DPN for carburized Ta-l8Ti-25W. Carburized tantalum exhibits a soft (195 DPN substrate immediately beneath the outer compounds. Carburizing of Ta-20Ti at 3,250 F for 6 hours results in the formation of a 2 mil thick carbide layer and a sharp transition in hardness at this boundary is noted. The 50 gram microhardness through the carbide is 1890, 1480 and 1560 DPN at a depth of 0.5, l, and 1.8 mils, respectively, and 370 DPN at a depth of 2.2 mils just below the carbide layer. Carburizing of molybdenum and tungsten also result in the formation of continuous carbide layers several mils thick.

Some examples of other carburized compositions that fall outside our invention because a multiphase structure existing essentially to the surface is not present are:

Cb-2Ti-2Mo pack carburized at 3,250 F for 7 hours;

The numerous carburized materials given in Table I falling within our invention should be considered as a series of examples and are presented in tabular form for brevity. Although graded multiphase structures extending essentially to the surface are observed for all, the morphology of the precipitated carbide phase varies and different microstructures are seen for some compositions. For example, varadium-titanium materials containing molybdenum and tungsten generally show fine carbide platelets rather than the structure of FIGS. 2 and 6. Zirconium may be substituted for titanium in our materials. Hafnium additions have been made both in a ternary material, Cb-30l-lf-15W, and a quaternary material, Cb-lSTi-lSHf-ZOW. We find that hafnium tends to promote the formation of a continuous carbide surface layer, especially at external corners where carburization is greatest. This tendency is reduced when the titanium and/or zirconium content is at least equal to the hafnium content.

Rhenium and chromium have been substituted for molybdenum and tungsten in some of the examples shown. Restricted amounts of other metallic or metalloid elements may be added and certain limited amounts of impurities may be present. Of the up-to-ten metals in our alloyed materials, rhenium is the only element that does not form a stable carbide. It may thus be expected that compositions higher in rhenium may be carburized without the formation of a continuous carbide layer. Carburized Cb-20Ti-25Cr shows a lower volume of hard carbide phase than the corresponding compositions with molybdenum, tungsten, or rhenium. Chromium additions in some cases may be limited because of this and because of the embrittling effect of high chromium additions to alloys.

These various metals hereof readily interalloy and carburized multiphase materials may be produced from alloys containing four or more metallic components. Restricted amounts of metallic or metalloid elements may also be added and certain limited amounts of impurities may be present. Our materials are required to be ternary or more complex. In such materials of this invention:

Group 1 content is 20 to 90 percent;

Group II content is 2 to 45 percent; and

Group III content is 2 to 55 percent.

Materials within the above ranges with higher titanium (greater than 35 percent) and lower columbium (lower than 40 percent) form coarser carburized structures. Also, we find that in some cases the amount of Group lll additions must be limited to 40 percent. A more preferred range is:

Group I content is 40 to 90 percent;

Group II content is 2 to 35 percent; and

Group III content is 2 to 40 percent.

Furthermore, we find that it is preferred to have at least 5 percent of both Group H and Ill additions rather than the minimum 2 percent and that it is desirable to decrease Group 1 content from the maximum of 90 percent to 85 percent. We find enhanced microstructures and properties by so doing.

The direct forming of the materials to shape prior to hardening is one of the advantages of this invention. Restricting metals of Group II such that the ratio Group ll/Group III is greater than one results in more fabricable alloys prior to carburizing. Thus, a fabricable, more preferred range hereof is given by:

Group 1 content is 40 to 85 percent;

Group [I content is 7.5 to 35 percent;

Group III content is 5 to 30 percent; and Ratio of Group Ill/Group III is greater than one.

Erosion and metal cutting tests confirm the good abrasion resistance of the materials of our invention. Erosion resistance was determined using a standardized tester that impinged high velocity alumina particles using argon gas as the propellant. Erosivity numbers are reported which represent an average erosion time required to develop a pit one mil in depth. The impringement angle is measured between the test specimen surface and particle stream. Results are shown in Table III:

TABLE Ill Carburization (F) Composition Cb-30Ti- Mo Ch-70Ti Stellitc 68 Carburized Cb-30Ti-20Mo falling within our inventon shows a much higher abrasion resistance than carburized Ch-70Ti having a continuous carbide layer. Our carburized Cb-30Ti-20Mo shows excellent erosion resistance compared to a commerical wear resistant material Stellite 6B (3Ni-2Si-3Ee-2Mn-30Cr-1.5Mo- 4.5W-0.9-l.4C-Balance Co).

The excellent abrasion resistance of the carburized materials was confirmed by employing the materialsas lathe cutting tool inserts for machining type 4340 steel of hardness Re 44. A standard negative rake tool holder was used, the feed and depth were 0.005 inch per revolution and 0.050 inch, the speed was 750 surface feet per minute (SFM), and two cubic inches of workpiece was removed. The following materials falling within our invention cut at 750 SFM:

Cb-30Ti-20Mo gas carburized at 3,350 F for 2 hours;

Cb-l7Ti-30W gas carburized at 3,350 F for 2 hours;

Cb-l7Ti-20W pack carburized at 3,350 F for 6 hours;

Cb-30Ti-20W pack carburized at 3,350 F for 8 hours;

Ta-12Ti-l5W pack carburized at 3,350 F for 7 hours.

Cb-Ti gas carburized at 3,350 F for 2 hours and "Fa-10W pack carburized at 3,250 F for seven hours were also tested at 750 SFM but failed immediately in testing. As noted above, both of these materials have continuous outer carbide layers and are excluded from our invention.

Metal cutting is a severe test that represents a complex interrelationship of adhesion and abrasion. For similar alloy compositions the carburized materials show different performance and offer certain advantages over nitrided materials. For example in cutting nodular iron, Cb-l7Ti-20W and Cb-17Ti-30W pack carburized at 3,250 F showed greater tool life at speeds up to 600 SFM as compared to Cb-l7Ti-20W nitrided at 3,585 F for 3 hours or Cb-17Ti30W nitrided at 3,500 F for 2 hours.

The carbon pick-up is in excess of 1 mg per square centimeter for all of the examples shown in Table I. However, the amount of carbon required for an equivalent surface hardness is substantially reduced when the material is used as a thin blade edge or sheet or as a thin coating or cladding. Also, such materials maybe used for a wide variety of applications requiring wear and abrasion resistance where the requirement for surface hardness or depth of hardening may be less than that required for metal cutting. Thus, for certain applications the carbon pick-up might be 0.1 to 1 mg per sq cm of surface area.

Our carburized materials having excellent abrasion resistance and utility as cutting tools must possess all of the following characteristics to be included in the present invention:

a. graded, as above described b. the microstructure is multiphase essentially to the surface c. carbon pick-up is at least 0.1 milligram per square centimeter of surface area d. the 25 gram load hardness measured on a cross sectional traverse in a zone between the surface and a depth of 0.5 mil is at least 800 DPN e. the composition must contain at least one metal from each of three groups wherein:

Group I is 20 to percent columbium, tantalum,

and vanadium;

Group ll is 2 to 45 percent titanium, zirconium and hafnium;

Group 111 is 2 to 55 percent molybdenum, tungsten,

rhenium and chromium.

In addition to carburizing we have combined carburizing plus nitriding treatments as shown in Table lV. Substantial weight pick-up occurred for all treatments and the desired multiphase structure is obtained. The relative weight pick-up of the secondary treatment is dependent upon the extent of reaction in the primary treatment. Microstructures are basically similar to those resulting from the primary treatment. The structure of Cb-30Ti-20W was coarser when carburized at 3,250 F compared to nitriding at the same temperature. A finer structure was obtained by nitriding prior to carburizing as compared with carburizing alone. A combined concurrent treatment in which the relative Although the alloys receptive to carburizing can be produced by coating or surface alloying techniques, t many uses involve the'forming and machining of a homogeneous alloy. One of the advantages in unility of these materials is our ability to form the metallic alloys by cold or hot working and/or to machine (or hone) to shape in the relatively soft condition prior to final carburizing. Only minimal distortion occurs during carburizing and replication of the starting shape and surface finish in excellent. The final surface is reproducible and is controlled by original surface condition, alloy composition, and carburizing treatment. For some applications, the utility would be enhanced by lapping, polish- "TABILE' IV COMPOSITION PRIMARY TREATMENT SECONDARY TREATMENT ORlG. WT. PICK-UP /O) ype F) (Type*) (g) g) Cb-30Ti-20W C 3250 8 N 3250 2 L 19 Cb-Ti-2OW N 3250 2 C 3250 7 0.8 24 6 Cb-30Ti-20W C 3250 8 N 3835 2 0.8 19 18 Cb-30Ti-20W N 3835 2 C 3250 8 0.7 44 3 Cb-l7Ti2()W C 3250 8 N 3250 2 1.] 2] 17 Cb-l 7Ti-20w N 3250 2 C 3250 8 0.8 30 7 der processing techniques in addition to the treatment of solid metal stock as described above. Furthermore, such alloys may be employed on another metal or alloy as a surface coating or cladding. Spraying and/or fusing the desired alloy onto the surface are included in the various coating methods available. Small other additions maybe made to our alloys to enhance the coatability. A variety of direct deposition methods may be employed or alternate layers could be deposited followed by a diffusion annealing treatment. The reacted material can be used as a mechanically locked insert or it can be bonded or joined by brazing, for example, to

a substrate.

Since our carburized and carbur-nitrided materials are in a thermodynamically mestastable condition, those skilled in the art will realize that a variety of heat treatments, including multiple and sequential treatments, can be used to modify the reaction product and resulting proper whether perfon'ned as part of the overall hardening reaction or as separate treatments. The materials can also be reacted at higher temperatures (and times) that normally would produce some embrittlement and then subsequently annealed in inert gas or various partial pressures of the reactive gas as a tem pering or drawing operation to improve toughness.

We have also observed the excellent corrosion resistance of both the alloys and the carburized materials in strong acids, and these materials could effectively be employed for applications requiring both corrosion and abrasion resistance. The materials can be employed for applications involving wear resistance and structural properties (hardness, strength, stiffness, toughness) at room and elevated temperatures. Other useful properties of the carburized materials include good electrical and thermal conductivity, high melting temperature,

and thermal shock resistance.

ing, or other finishing operations after carburization. The carburized surface is quite hard but only a small amount of material removal is required to produce a highly finished surface.

The excellent cutting properties and wear resistance of the carburized and carbur-nitrided materials can be effectively employed with the other useful properties of the alloys and reacted materials to produce a wide range of products. Some of these are: single point cutting tools, multiple point cutting tools (including rotary burrs, files, routers and saws), drills, taps, punches, dies for extrusion, drawing, and other forming operations, armor, gun barrel liners, impeller or fan blades, EDM (electrical Discharge Machining) electrodes, spinnerets, guides (thread, wire, and other), knives, razor blades, scrapers, slitters, shears, forming tools, grinding media, pulverizing hammers and rolls, capstans, needles, gages (thread, plug, and ring), bearings and bushings, nozzles, cylinder liners, tire studs, pump parts, mechanical seals such as rotary seals and valve components, engine components, brake plates, screens, feed screws, sprockets and chains, specialized electrical contacts, protection tubes, crucibles, molds and casting dies, and a variety of parts used in corrosion-abrasion environments in the paper-making or petrochemical industries, for example.

It will be understood that various modifications and variations may be affected without departing from the spirit or scope of the novel concepts of our invention.

We claim as our invention:

1. As an article of manufacture a cutting tool for machining, said cutting tool consisting essentially of a carburized material with the carbon concentration lessening inwardly from the surface having a graded multiphase structure consisting of at least two distinct interspersed phases extending substantially to the surface, said cutting tool being formed of an alloy consisting essentially of at least one metal of each of Groups I, II and III and wherein:

a. Group I is columbium, tantalum, and vanadium and is present in amounts ranging from 20 to percent;

b. Group II is titanium, zirconium and hafnium and is present in amounts ranging from 2 to 45 percent;

c. Group III is molybdenum, tungsten, rhenium and chromium and is present in amounts ranging from 2 to 55 percent;

d. the carbon pick-up is at least 0.1 milligram per square centimeter of surface area;

e. the microhardness in the zone between the surface and up to 0.5 mil below the surface is at least 800 diamond pyramid numerals;

f. said cutting tool has at least 25 percent by volume of a carburized hard phase at the surface thereof; and

g. which article of manufacture when adequately carburized is capable of removing 2 cubic inches of steel having a Rockwell C hardness of 44 at a cutting speed of 750 surface feet per minute.

2. The cutting tool as defined in claim 1 wherein the carbon pick-up is at least one milligram per square centimeter of surface area.

3. The cutting tool defined in claim 1 wherein Group ll consists of titanium, zirconium, and mixtures thereof, and hafnium is present in amounts less than the combined total of said titanium and zirconium.

4. The cutting tool as defined in claim 1 wherein up to 25 percent of the carbon content thereof is replaced by boron.

5. The cutting tool as defined in claim 1 wherein:

a. Group ll is titanium and zirconium; and

b. Group 111 is molybdenum, tungsten and rhenium.

6. The cutting tool as defined in claim 5 wherein Group I is columbium.

7. The cutting tool as defined in claim 1 wherein: Group I content ranges from 40 to 90 percent; Group ll ranges from 2 to 35 percent; Group III ranges from 2 to 40 percent; and, hafnium, if present of Group II, is present in amounts less than titanium and zirconium.

8. The cutting tool as defined in claim 7 wherein:

Group II is titanium and zirconium; and Group III is molybdenum, tungsten and rhenium.

9. The cutting tool as defined in claim 1 wherein: Group I content ranges from 40 to percent; Group II content ranges from 5 to 35 percent; and Group III content ranges from 5 to 55 percent.

10. The cutting tool as defined in claim 9 wherein hafnium, if present, is present in amounts less than titanium, zirconium, and mixtures thereof.

11. The cutting tool as defined in claim 9 wherein Group II is titanium, zirconium and mixtures thereof.

12. The cutting tool as defined in claim 9 wherein Group II is titanium.

13. The cutting tool as defined in claim 1 wherein: Group 1 content ranges from 40 to 85 percent; Group II content ranges from 7.5 to 35 percent; Group III content ranges from 5 to 30 percent; and The ratio of Group II content to Group III content is greater than one.

14. The cutting tool as defined in claim 13 wherein hafnium, if present, is present in amounts less than titanium, zirconium and mixtures thereof.

15. The cutting tool as defined in claim 13 wherein Group II is titanium, zirconium and mixtures thereof.

16. The cutting tool as defined in claim 15 wherein Group III is molybdenum, tungsten, rhenium and mixtures thereof and wherein the carbon pick-up is at least one milligram per square centimeter of surface area.

17. The cutting tool as defined in claim 16 wherein up to 25% of the carbon is replaced by boron.

18. The cutting tool as defined in claim 13 wherein Group II is titaniun and zirconium and Group III is molybdenum, tungsten, and rhenium.

19. The cutting tool as defined in claim 18 wherein Group I is columbium, vanadium and mixtures thereof and Group II is titanium, zirconium and mixtures UNITEl) STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTIGN PATENT NO. 3, 830, 670 DATED August 20, 1974 INVENTOR(S) I Ray J. Van Thyne and John J. Rausch It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below;

Column 3, line 37, "Ta-301;" should read Ta 3O Ti Column 3, line 39, "Ta 20 T1 10 Mo" should read Ta 2O Ti Column 4, line 43, after 'chunk" insert carbon Column 5, below TABLE II, insert H C Cracking M Hardness in matrix Column 7, line 51, "Ch" should read --Cb Column 7, line 54, "Ee" should read Fe Column 9, line 50, "proper" should read properties Column 10, line 4, "unility" should read M utility Signed and Sealed this Twenty-eighth D ay Of June 1977 [SEAL] A ttest:

RUTH C. MASON Arresting Officer C. MARSHALL DANN Commissioner uj'Parenrs and Trademarks 

2. The cutting tool as defined in claim 1 wherein the carbon pick-up is at least one milligram per square centimeter of surface area.
 3. The cutting tool defined in claim 1 wherein Group II consists of titanium, zirconium, and mixtures thereof, and hafnium is present in amounts less than the combined total of said titanium and zirconium.
 4. The cutting tool as defined in claim 1 wherein up to 25 percent of the carbon content thereof is replaced by boron.
 5. The cutting tOol as defined in claim 1 wherein: a. Group II is titanium and zirconium; and b. Group III is molybdenum, tungsten and rhenium.
 6. The cutting tool as defined in claim 5 wherein Group I is columbium.
 7. The cutting tool as defined in claim 1 wherein: Group I content ranges from 40 to 90 percent; Group II ranges from 2 to 35 percent; Group III ranges from 2 to 40 percent; and, hafnium, if present of Group II, is present in amounts less than titanium and zirconium.
 8. The cutting tool as defined in claim 7 wherein: Group II is titanium and zirconium; and Group III is molybdenum, tungsten and rhenium.
 9. The cutting tool as defined in claim 1 wherein: Group I content ranges from 40 to 85 percent; Group II content ranges from 5 to 35 percent; and Group III content ranges from 5 to 55 percent.
 10. The cutting tool as defined in claim 9 wherein hafnium, if present, is present in amounts less than titanium, zirconium, and mixtures thereof.
 11. The cutting tool as defined in claim 9 wherein Group II is titanium, zirconium and mixtures thereof.
 12. The cutting tool as defined in claim 9 wherein Group II is titanium.
 13. The cutting tool as defined in claim 1 wherein: Group I content ranges from 40 to 85 percent; Group II content ranges from 7.5 to 35 percent; Group III content ranges from 5 to 30 percent; and The ratio of Group II content to Group III content is greater than one.
 14. The cutting tool as defined in claim 13 wherein hafnium, if present, is present in amounts less than titanium, zirconium and mixtures thereof.
 15. The cutting tool as defined in claim 13 wherein Group II is titanium, zirconium and mixtures thereof.
 16. The cutting tool as defined in claim 15 wherein Group III is molybdenum, tungsten, rhenium and mixtures thereof and wherein the carbon pick-up is at least one milligram per square centimeter of surface area.
 17. The cutting tool as defined in claim 16 wherein up to 25% of the carbon is replaced by boron.
 18. The cutting tool as defined in claim 13 wherein Group II is titaniun and zirconium and Group III is molybdenum, tungsten, and rhenium.
 19. The cutting tool as defined in claim 18 wherein Group I is columbium, vanadium and mixtures thereof and Group II is titanium, zirconium and mixtures thereof. 